a) Field of the Invention
The present invention generally relates to integrated circuits, and more specifically, to a temperature sensor for an integrated circuit.
b) Background
Temperature sensing has been widely used in integrated circuits.
One example is a temperature compensated crystal oscillator (TCXO). A temperature sensor is used to compensate the crystal oscillator so the crystal oscillator's frequency is much more stable under a environment with varying temperature than a crystal oscillator without a temperature compensation scheme. Temperature compensated crystal oscillators have been widely used in commercial digital communications applications.
Another example is a microprocessor using a integrated temperature sensor to sense the die temperature in order to prevent the microprocessor from overheating and thus cause malfunctioning. As the clock frequency of a microprocessor increases, the microprocessor's self-heating issues becomes more and more important.
Yet another example of using a integrated temperature sensor is a DRAM chip. A DRAM chip needs to adjust its refresh period based on sensed chip temperature in order to avoid data loss.
Yet another use of a temperature sensor is for the temperature control of consumer electronics, such as home electronics and automobiles.
A typical integrated temperature sensor utilizes a temperature sensing diode to generate a temperature dependent voltage, then uses an analog-to-digital converter (ADC) to convert the temperature dependent voltage into digital form so that the temperature can be calculated. However, an analog-to-digital converter usually consume a fairly large chip space and fairly large power, and its circuitry is rather complex. Furthermore, the accuracy of the analog-to-digital converter is often affected by digital switching noises, and self heating.
Hence, a need exists to provide a low cost, high accuracy integrated temperature sensor, whose power consumption should be minimized to be applicable on battery powered portable electronic devices like cellular phones, PDAs and laptops.